The present invention relates to a sealing ring apparatus for a fluid valve having a piston reciprocating within a cylinder. Fluid valves of this type include a cylinder having inlet/outlet passageways external to the cylinder. A piston having a hollow front end for receiving a pressurized fluid includes inlet/outlet ports through its side walls. A connecting rod attached to the rear end of the piston provides reciprocating motion of the piston within the cylinder to seat and unseat a valve cone formed around the front end of the piston and adapted to contact a valve seat. The fluid valve is opened by reciprocation of the piston to unseat the valve cone and align the inlet/outlet ports of the piston with the inlet/outlet passageways. A ring comprising resilient material is packed in an annular groove around the rear end of the piston to provide a seal between the piston and the inside surface of the cylinder.
Known sealing rings for this type of fluid valve have the disadvantage that the ring packing arranged around the surface of the piston must be under a considerable amount of pressure for a reliable seal to be achieved. As a result, frictional forces are created which hinder the piston movement and also lead to considerable wear of the structural parts. Thus, there is a need for a piston sealing apparatus which provides a reliable seal when the fluid valve is closed but which creates low frictional forces when the piston is reciprocated.